It seems to me that one of the simplest rules to follow when doing knowledge work (or symbolic analyzing, or being creative) is this: don’t try to work only on little things when your mind is able to do big things; and don’t try to work on big things when your mind is only able to do little things.
This is a simple principle but it’s amazing how easy it is to not follow, and how much better you can use your time if you do.